A cost-effective strategy to construct highly effective flame-retardant coatings of modified epoxy resin/layered double hydroxide/zinc borate for polystyrene foam

Abstract

The flammability of expanded polystyrene (EPS) foams severely limits their range of applications. Although several methods have been used to improve their flame-retardant properties, there is still a lack of an efficient and cost-effective strategy to ensure their fire safety. In this work, utilizing water-based polyurethane modified epoxy resin (WEPU), layered double hydroxide (LDH) and zinc borate (ZnB) as raw materials, a highly efficient flame-retardant coating was constructed on the surface of EPS to improve its mechanical properties, flame retardancy and smoke suppression capabilities. The application of a flame-retardant coating (LDH: ZnB = 1:3) increased the compressive strength of the original EPS by 68.33 %, increased the char yield from 0.14 % to 46.43 %, increased the oxygen index to 38.8 %, enabled the vertical flame test to reach the UL-94 V-0 level, reduced the peak heat release rate by 53.02 %, reduced the peak smoke production rate by 61.45 %, and the coating exhibited excellent adhesion and water resistance. The evolution characteristics of molecular number, system potential energy, and product distribution during the combustion process of WEPU/LDH/ZnB coatings were obtained through molecular simulation. Furthermore, the synergistic flame-retardant mechanism between the condensed and gas phases of these coatings was elucidated at the microscopic level.